Chair for an exercise ball



FIG. 1 is a perspective view of a front, top, and a first side of an ornamental design for a chair holding an exercise ball;

FIG. 2 is a front elevational view of the chair of FIG. 1;

FIG. 3 is a rear elevational view of the chair of FIG. 1;

FIG. 4 is an elevational view of a second side of the chair of FIG. 1;

FIG. 5 is an elevational view of the first side of the chair of FIG. 1;

FIG. 6 is a top plan view of the chair of FIG. 1; and,

FIG. 7 is a bottom elevational view of the chair of FIG. 1.

The broken lines in the drawings depict environmental subject matter only and form no part of the claimed design. 

CLAIM The ornamental design for a chair for an exercise ball, as shown and described. 